cache the symbolize_keys lookup in C
cache the symbolize_keys lookup in C

kou/ffi-yajl,h4ck3rm1k3/ffi-yajl,h4ck3rm1k3/ffi-yajl,chef/ffi-yajl,chef/ffi-yajl,kou/ffi-yajl,chef/ffi-yajl,h4ck3rm1k3/ffi-yajl,kou/ffi-yajl